It's been nearly four years since Google sold its first Nexus device running Android, the Nexus One smartphone, in January 2010.

In smartphone terms, four years can seem like a decade, especially when most smartphones turn over in two years.

Google's Nexus One smartphone first appeared four years ago.

So it's certainly fair to ask: Has Google's Nexus smartphone and tablet series -- featuring no software modifications beyond basic Android and coming unlocked from carriers -- had much of an impact, if not in sales, then in the overall market?

During the last four years, the total Android market, including devices made by several major manufacturers, has grown to dominate global smartphone sales, reaching about 80% of the market, while Android on tablets outdistanced Apple's iPads in 2013, according to IDC.

By comparison, most analysts don't have specific numbers for Nexus device shipments or sales, although they are considered too small to have had a significant impact.

"Google-branded smartphones have not made a material impact in market share. They are in the 'other' category of global smartphones," said Patrick Moorhead, an analyst at Moor Insights & Strategy. The top five makers in recent quarters are Samsung, Apple (on iOS only), Huawei, Lenovo and LG Electronics.

Yankee Group surveyed 16,000 U.S. smartphone customers throughout much of 2013 and found the percentage of those who bought a Google Nexus smartphone in the previous six months was below 5%, while the percentage owning one was less than 1%, but improved in August to 1.04%. The margin of error in its polling is about 1%.

"Google Nexus devices aren't having much of an impact on the market," said Carl Howe, a Yankee Group analyst.

The same can be said of Nexus tablets in terms of market share of all Android tablets. But that misses the point: Robust sales are not Google's ultimate goal in making Nexus gear.

Google's original intent when it devised the Nexus line was to show what an all-Google user experience would be like and to inspire Android makers and developers to make better phones, tablets and Android apps.

"The Nexus line is a hedge against indifference," Moorhead said. "It sends a message to manufacturers that if they can't develop competitive Android products, Google will on their own."

The Nexus One

The original Nexus One, manufactured by HTC, ran Android 2.1, also known as Eclair. Since 2010, Google has ushered in an array of relatively inexpensive yet full-featured smartphones, including the latest, the Nexus 5, built by LG and running Android 4.4 KitKat, that was introduced on Oct. 31.

There are now Nexus tablets in various sizes as well, starting with the first generation Nexus 7, a 7-in. tablet featuring Android 4.1, that went on sale in July 2012.

Nexus devices can be purchased online in the Google Play store unlocked or with any carrier's cellular service long-term contract. For example, the new Nexus 5 smartphone starts at $349 unlocked for 16 GB, running Android 4.4 (KitKat), but it can cost much less with a carrier contract which usually requires a two-year commitment.

The new Google Nexus 7, a 7-in. tablet, starts at $229 for a 16 GB Wi-Fi model. Made by Asus, it offers optional LTE. The Google Nexus 10, a 10-in. tablet, starts at $399 for 16GB over Wi-Fi. Both received Android 4.4 KitKat updates in mid-November.

Temporary shortages of Nexus products could lead buyers to assume the devices are very popular, although analysts said it's too hard to judge if the shortage is due to a deliberately limited inventory in the first place or robust sales. Google hasn't commented.

Even if Nexus sales aren't spectacular, Google is making a market impact in driving home its point of showing how a stripped-down Android OS can be valuable to some consumers, while also indirectly lowering costs for smaller cell-phone makers in emerging markets.

Lower costs with basic Android

Smaller manufacturers that produce white-box devices for emerging markets in Asia and other parts of the world do little to enhance Android, if they do anything at all, noted Jack Gold, an analyst at J. Gold Associates.

"These vendors are having an impact, especially at the low end, so in that sense, vanilla-flavored Android [with no or few software modifications added] is having an impact," Gold said. "Most brand-name vendors do modify the base Android code before releasing their products."

Some white-box vendors can sell Android tablets unlocked at less than $100, Gold said.

With smartphones, meanwhile, the unlocked Android approach has enabled a number of newer manufacturers to enter the smartphone market by using a variety of lower cost, turnkey processes that rely on standard chipsets for processing and related functions, analysts from research firm IDC said.

That approach has helped the average selling price of a smartphone to fall to $337 globally in 2013, down nearly 13% from 2012, IDC said. By 2017, smartphone average prices should drop to to $265 globally. (The average selling price of the iPhone is $577, according to Gartner.)

Nexus smartphones, such as the Nexus 5, are close to the average selling price globally, although most experts place the Nexus phones at the high end in terms of features, such as large displays and fast processors. "Nexus smartphones have a lot of hardware bells and whistles at the high end to serve a select segment that includes tinkerers and people who like to mess around with Android," said IDC analyst Ramon Llamas.

These newer manufacturers adopting Android (although not necessarily basic Android) include Chinese smartphone vendors ZTE, Xiaomi, which recently hired Google executive Hugo Barra, and Yulong, which makes Coolpad smartphones like the Quattro 4G that ran Android 2.3 (Gingerbread) when it launched in late 2012 in the U.S.

Other Nexus benefits

Google not only has set the stage for this smaller-vendor manufacturing process with the Nexus series, it has set up greater value for the 1 million apps in the Google Play store, which become available to more buyers as Nexus sales increase.

In addition, selling unlocked Nexus devices has, to some extent, empowered buyers. They can have a choice of a carrier -- assuming the device's cellular network will work with various carriers. This more open approach is widely used in Europe and other regions where GSM wireless dominates, but now LTE is becoming a common wireless connection across major U.S. carriers as well.

Some wireless carriers won't give a full range of services and apps to customers who use unlocked Nexus devices and then buy a carrier's SIM card for cellular connectivity. "Will the carriers allow you to use any app you choose, or will they require that you download some specific app, such as their videoconferencing service? It's a gray area," Gold said.

Even with some limits placed by carriers on Nexus usage, Google seems solidly on track to add more Nexus smartphones and tablets in the future. The roadmap is not public, however.

Nexus-Android pushes emergence of Tizen

Google's Nexus approach has helped challenge wireless carriers that fear the overall growth of Google and have pushed for big device makers like Samsung to find alternatives to Android.

Tizen, an open-source operating system that attracted attention at Samsung's recent developer conference, has emerged as a potential challenger to Android, and therefore to Nexus products.

"Tizen is a hedge against Android's strength," Moorhead said. "Carriers know that there are certain buyers that want an unlocked phone like the Nexus, and as long as that number remains small, the carriers are OK. But I think carriers are concerned that Google is getting too powerful, which is why they are interested in Tizen in the long term."

Four years into the life of Nexus on basic Android, it's ironic that Android was originally seen as the disrupter to other dominant smartphone operating systems. "Funny how Android was originally a hedge [against] Microsoft, BlackBerry and Nokia," Moorhead said.